• Deepstop (see 3.17 Safety stops and deepstops)
• Air time (see 3.2 Air time) 3.12.2 Nitrox mode
NITROX mode is for diving with oxygen-enriched gas mixtures.
Diving with nitrox allows you to increase bottom times or reduce the risk of decompression illness. However, when the gas mix is altered or depth increased, the oxygen partial pressure is generally increased. Suunto D4i provides you with information to adjust your dive and stay within safe limits.
NITROX mode has the following settings
• Nitrox (gas mixture): define up to three mixes
• Personal/altitude adjustment (see 3.16 Personal and altitude adjustments)
• Depth alarm (see 3.10 Depth alarm)
• Dive time alarm (see 3.14 Dive time alarm)
• Sample rate (see 3.18 Sample rate)
• Deepstop (see 3.17 Safety stops and deepstops)
• Air time (see 3.2 Air time)
In NITROX mode, both the percentage of oxygen in your tank and the oxygen partial pressure limit must be entered into Suunto D4i. This ensures correct nitrogen and oxygen calculations and the correct maximum operating depth (MOD), which is based on your entered values.
The default oxygen percentage (O2%) setting is 21% (air) and oxygen partial pressure (PO2) setting is 1.4 bar (20 psi). 36
To modify gas mix settings:
1. While in Nitrox mode, keep [DOWN] pressed. 2. Press [SELECT] to enter the Nitrox setting.
3. Scroll to Mix1, Mix2 or Mix3 as desired and press [SELECT]. 4. Define the selected mix as Primary, Secondary or Off with [UP]
or [DOWN] and confirm with [SELECT].
53.6 Mix1 Primary
5. Adjust the blinking O2 value with [DOWN] or [UP] to match the oxygen % of your tank and accept with [SELECT].
6. Adjust the blinking PO2 (oxygen partial pressure) value with [DOWN] or [Up] and confirm with [SELECT].
7. Adjust other mix settings as needed. 8. Press [MODE] to exit.
NOTE: If the oxygen content of a mix is set to 22% or above,
the setting value remains until changed. It does not automatically revert back to 21%.
3.12.3 Free mode
With Free mode, Suunto D4i can be used as a freediving instrument. The dive time is indicated in minutes and seconds in the center of the display.
The free dive starts at 1.2 m (4 ft) and ends when your depth is less than 0.9 m (3 ft).
Free mode has the following settings:
• Depth notifications (see 12.3.1 Depth notifications)
• Depth alarm (see 3.10 Depth alarm)
• Dive time alarm (see 3.14 Dive time alarm)
• Surface timer (see 3.20 Surface and no-fly time )
• Sample rate (see 3.18 Sample rate) 3.12.3.1 Depth notifications
You can define up to five independent depth notifications for freediving, for example, to alert you to start free falling or mouth filling. Each notification has a defined depth and can be turned on or off.
When you reach the notification depth, the backlight blinks and the low priority audible alarm sounds.
To define depth notifications:
1. While in Free mode, keep [DOWN] pressed. 2. Press [SELECT] to enter the Depth Notify settings.
3. Scroll through the notifications with [DOWN] or [UP] and enter a notification with [SELECT].
4. Press [DOWN] or [UP] to toggle the notification On/Off and confirm with [SELECT].
5. Adjust the depth with [DOWN] or [UP] and confirm with [SELECT].
6. Scroll to the next notification to modify or press [MODE] to exit. 3.12.3.2 Surface countdown timer
While freediving, you can use the surface countdown timer to help you prepare yourself for you next dive. Suunto D4i starts the countdown as soon as you reach 1.2 m (4 ft).
To set the surface countdown timer:
1. While in Free mode, keep [DOWN] pressed. 2. Press [UP] to scroll to Surf. Time Notify.
3. Press [DOWN] or [UP] to toggle the timer on and confirm with [SELECT].
4. Adjust the countdown duration with [DOWN] or [UP] and conform with [SELECT].
5. Press [MODE] to exit.
3.13 Dive planning mode
The dive planning mode PLAN NoDeco can be used to plan a dive that does not require decompression. You enter the depth of your upcoming dive, and Suunto D4i calculates the maximum time you can stay at that depth without requiring decompression stops. The dive plan takes into account:
• any calculated residual nitrogen
• dive history from the past four days
To plan dives:
1. Press [MODE] until you see PLAN NODEC.
2. The display briefly shows your remaining desaturation time before continuing to the planning display.
3. Press [DOWN] or [UP] to scroll your upcoming dive depths. The depth moves in 3 m (10 ft) increments from 9 m – 45 m (30 ft – 150 ft). The no-decompression time limit for the selected depth is shown in the center of the display.
If you have dived at least once with Suunto D4i, the SURFTIME + field appears. You can adjust the surface time with [UP]. 4. Between consecutive dives, you can press [SELECT] to adjust
surface time. 5. Press [MODE] to exit.
NOTE: The dive planning mode is disabled if the dive computer
is in an error state (see 3.15 Error state (algorithm lock)) or if the dive mode is off or in Gauge mode.
3.14 Dive time alarm
The dive time alarm can be activated and used for several purposes to add to your diving safety. It is simply a countdown timer in minutes.
To set the dive time alarm:
1. While in a relevant dive mode, keep [DOWN] pressed. 2. Press [DOWN] or [UP] to scroll to ALARM TIME.
3. Press [UP] to toggle the alarm on and press [SELECT] to confirm. 40
4. Adjust the duration with [UP] or [DOWN] and accept with [SELECT].
5. Press [MODE] to exit.
3.15 Error state (algorithm lock)
Suunto D4i has warning indicators that alert you to react to certain situations that would significantly increase the risk of DCI. If you do not respond to these warnings, Suunto D4i enters an error state and shows Er on the display. This indicates that the risk of DCI has greatly increased.
If you omit decompression stops for longer than three (3) minutes, the RGBM algorithm is locked for 48 hours. When the algorithm is locked, no algorithm information is available and ER is shown instead. Locking the algorithm is a safety feature, highlighting that the algorithm information is no longer valid.
In such a condition, you should descend back below the ceiling level to continue the decompression. If you fail to do so within three (3) minutes, Suunto D4i locks the algorithm calculation and displays ER instead, as shown below. Note that the ceiling value is no longer present.
In this state, you significantly increase your risk of decompression sickness (DCS). Decompression information is not available for the next 48 hours after surfacing.
It is possible to dive with the device when the algorithm is locked, but instead of the decompression information, ER is shown. If you dive again in this error state, the algorithm lock time resets to 48 hours when you surface.
3.16 Personal and altitude adjustments
There are several factors that can affect your susceptibility to DCS. Such factors vary between divers and from one day to another. The personal factors which tend to increase the possibility of DCS include:
• exposure to cold water - less than 20°C (68 °F)
• below average physical fitness level
• fatigue
• dehydration
• stress
• obesity
• patent foramen ovale (PFO)
• exercise before or after dive
The three-step personal setting can be used to adjust the algorithm to fit your DCS susceptibility.
Personal adjustment Explanation
0 Ideal conditions (default value). 42
Personal adjustment Explanation
1 Conservative. Some risk factors orconditions exist. 2 More conservative. Several risk factors
or conditions exist.
In addition to the personal setting, Suunto D4i can be adjusted for diving at different altitudes. This adjusts the decompression calculation according to the selected altitude adjustment.
Altitude adjustment Explanation
0 0 – 300 m (0 – 980 ft) (default) 1 300 – 1500 m (980 – 4900 ft) 2 1500 – 3000 m (4900 – 9800 ft) To change the personal and altitude adjustment settings: 1. While in a dive mode, keep [DOWN] pressed.
2. Press [SELECT] to enter Personal Altitude settings.
3. Press [UP] to change the Personal adjustment and confirm with [SELECT].
4. Press [UP] to change the Altitude adjustment and confirm with [SELECT].
5. Press [MODE] to exit.
WARNING: Traveling to a higher altitude can temporarily cause
changes to the equilibrium of dissolved nitrogen in the body. It is recommended that you acclimatize to the new altitude by waiting at least three (3) hours before diving.
3.17 Safety stops and deepstops
Safety stops are widely considered good diving practice and are a critical part of most dive tables. The reasons for performing a safety stop include: reducing sub-clinical DCI, microbubble reduction, ascent control, and orientation before surfacing.
Suunto D4i displays two different types of safety stops: recommended and mandatory.
With every dive over 10 meters (30 feet), there is a three-minute countdown for the recommended safety stop. This stop is taken in the 3-6 m (10-20 ft) range. Suunto D4i shows a STOP icon and a three-minute countdown.
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NOTE: When deepstops are enabled, the length of mandatory
safety stops is indicated in seconds.
When the ascent rate exceeds 10 m (33 ft) per minute for more than five consecutive seconds, the microbubble build-up may be more than is allowed for in the decompression model.
In this situation, Suunto D4i adds a mandatory safety stop to the dive. The time of this stop depends on the speed violation of the ascent rate.
The STOP icon is shown in the display. When you reach the depth zone between 6 m and 3 m (18 ft and 9 ft) the following is displayed:
1. CEILING and STOP 2. Ceiling depth 3. Safety stop time
Wait at the ceiling until the mandatory safety stop warning disappears.
WARNING: NEVER ASCEND ABOVE THE CEILING! You must not
ascend above the ceiling during your decompression. In order to avoid doing so by accident, you should stay somewhat below the ceiling.
Deepstops activate when you dive deeper than 20 m (65.6 ft). If the dive timer is on the screen when deepstop activates, the timer is replaced with deepstop.
After deepstop is over, the user can change between deepstop and the timer by long pressing the MODE button.
Deepstops are presented the same way as safety stops. Suunto D4i notifies you that you are in the deepstop area by displaying:
• CEILING in the top
• DEEPSTOP in the center row
• Stop depth
• Countdown timer
Deepstop is on by default in Air and Nitrox modes. To turn deepstop off:
1. While in a dive mode, keep [DOWN] pressed. 46
2. Press [DOWN] to scroll to Deepstop and enter with [Select]. 3. Press [UP] to toggle on/off.
4. Press [MODE] to exit.
3.18 Sample rate
The sample rate controls how often information from the dive is saved to the active log. The default sample rate is 20 seconds in air and nitrox modes, and 2 seconds in free dive mode.
To change the sample rate:
1. While in a dive mode, keep [DOWN] pressed. 2. Press [UP] to scroll to Sample Rate and press [SELECT]. 3. Press [DOWN] or [UP] to change the rate and confirm with
[SELECT].
4. Press MODE to exit.
The sample rate options in air and nitrox modes are: 10, 20, 30 and 60 seconds.
The sample rate options in free dive mode are: 1, 2 and 5 seconds.